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Vulnerability · Published Jul 8, 2026 · Assigned by GitHub_M

CVE-2026-58214NATS Server: MQTT subscribe ACL bypass via $MQTT.deliver.pubrel prefix (incomplete fix for CVE-2026-33217)

Medium 4.3

In plain English

A medium-severity incorrect authorization in nats-server from nats-io. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 29% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)4.3Medium
Exploit odds (30 days)0.3%top 71.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, an authenticated MQTT client could subscribe to the internal $MQTT.deliver.pubrel subject family, bypassing configured subscribe permissions and exposing MQTT QoS2 protocol metadata for sessions in the account. This issue is fixed in versions 2.14.3 and 2.12.12.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12nats-serverno fix listedDEBIAN-CVE-2026-58214
Debian:13nats-serverno fix listedDEBIAN-CVE-2026-58214
Debian:14nats-server2.14.3-1DEBIAN-CVE-2026-58214
Ubuntu:24.04:LTSnats-serverno fix listedUBUNTU-CVE-2026-58214
Ubuntu:25.10nats-serverno fix listedUBUNTU-CVE-2026-58214
Ubuntu:26.10nats-serverno fix listedUBUNTU-CVE-2026-58214

Affected products (as reported)

VendorProductVersions
nats-io nats-server < 2.12.12>= 2.14.0-RC.1, < 2.14.3

Weakness: CWE-863 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

References